1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology, and more particularly, to a transmitter/receiver that supports differential signaling.
2. Description of the Related Art
Communication systems transmit, receive, store, and search a great amount of data. In complicated systems, transmitters/receivers (Tx/Rx) used for data transmission between integrated circuits (ICs) should perform a high speed operation while supporting various signaling schemes, generate minimum noise, be tolerant to interference, consume low power, and occupy a minimum area on an IC.
Transmitters/receivers according to the conventional art typically support only one signal type, that is, single-ended signaling.
FIG. 1 is a circuit diagram illustrating a transmitter/receiver using a single-ended signaling scheme according to the conventional art.
Referring to FIG. 1, a transmitter 110 and a receiver 120 may include buffers 111 and 121, respectively. The receiver 120 physically uses the same reference signal Vref in receiving a signal OUT outputted from the transmitter 110. Therefore, when the transmitter 110 transmits N signals, since N+1 signal lines (N receiving lines+one reference signal line) are necessary, the cost for circuit configuration is low. However, a concern exists in that the receiver 120 is sensitive to noise.
To resolve this concern of the single-ended signaling scheme, a differential signaling scheme is used.
FIG. 2 is a circuit diagram illustrating a transmitter/receiver using a differential signaling scheme according to the conventional art.
Referring to FIG. 2, a transmitter 210 terminates differential signals D and DB to a first power supply terminal VDD or a second power supply terminal VSS through a buffer 211, and outputs signals OUT and OUTB. Accordingly, a receiver 220 may operate by receiving (IN and INB) which are the differential signals OUT and OUTB outputted from the transmitter 210.
As described above, in the differential signaling scheme when N signals are transmitted/received, signals having phases opposite to those of the N signals are sent together with the N signals, therefore signal lines increase by a factor of two. Furthermore since the difference between the two signals is constant, electromagnetic interference to the signals is reduced when the signals are toggled, so that the differential signaling scheme is advantageous in high speed transmission. However, since two signals having opposite phases are terminated a the first power supply terminal VDD or the second power supply terminal VSS, current is always consumed regardless of signal phase.